Self-sustained oscillations of the current have been observed and simulated in a doped GaAs-AlAs superlattice under voltage control. Depending on the applied bias the detected frequencies vary betwen 250 kHz at low voltages and 20 MHz at high voltages. Amplitude and frequency decrease with increasing carrier density until, at very high excitation densities, stable electric-field domains are formed. A discrete drift model reproduces the current oscillations and shows that they can be attributed to the spatial oscillation of the boundary between the two domains.

• Received 31 May 1995

DOI:https://doi.org/10.1103/PhysRevB.52.13761